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What are the risk factors for childhood leukemia?

The exact cause of most cases of leukemia is not known. But doctors have found that this cancer is linked to a few risk factors.

A risk factor is something that increases a person’s chance of getting a disease. Different cancers have different risk factors. Some risk factors, such as smoking, can be controlled. Others, like a person’s age or family history, can’t be changed.

Lifestyle risk factors such as diet, body weight, exercise, and tobacco use play a major role in many adult cancers. But these factors often take many years to affect cancer risk, and they are not thought to play much of a role in childhood cancers, including leukemias.

There are a few known risk factors for childhood leukemia. But most children with leukemia do not have any known risk factors, and the cause of their cancer is not known at this time.

Genetic risk factors

Genetic risk factors are those that are part of our DNA. DNA is the substance that carries our genes, the instructions for nearly everything our cells do. While we don’t know the exact cause of most cases of leukemia, during the past few years scientists have made great progress in learning how certain changes in DNA can cause bone marrow stem cells to develop into leukemia. These changes are most often inherited from our parents. But while some genetic factors increase the risk of childhood leukemia, most cases of leukemia are not linked to any known genetic causes.

Children with certain genetic conditions such as Li-Fraumeni syndrome, Down syndrome, Klinefelter syndrome, and others have an increased risk of leukemia. (A syndrome is a cluster of signs and symptoms that point to a certain disease or disorder.) Other genetic diseases that cause children to be born with an abnormal immune system may also increase their risk of getting leukemia.

Brothers and sisters of children with leukemia have a slightly higher chance of getting leukemia, although the overall risk is still low. The risk is much higher among identical twins.

Having a parent who develops leukemia as an adult does not seem to raise a person’s risk of leukemia.

Lifestyle risk factors

For the most part, lifestyle risk factors such as diet and exercise play a very small role (if any) in childhood cancer risk, even though they are important in adult cancers. Some studies have suggested that a mother drinking a lot of alcohol during pregnancy may increase the risk of leukemia in her child, but not all studies have found such a link.

Environmental risk factors

Environmental risk factors are things around us such as radiation and certain chemicals, which increase the risk of getting diseases like leukemia.

Radiation

Exposure to high levels of radiation is a risk factor for childhood leukemia. Japanese atomic bomb survivors had a much higher risk of getting the AML type of leukemia. There may also be some risk if a fetus is exposed to radiation in the first months of the mother’s pregnancy, although the extent of the risk is not clear.

It is not known how much risk there might be when children are exposed to lower levels of radiation, such as from x-rays or CT scans. Any increase in risk is likely to be small, but to be safe, most doctors do not order these tests for pregnant women or children unless they are really needed.

Exposure to chemo drugs and certain other chemicals

Children and adults who were treated with chemo for other cancers have a higher risk of getting a second cancer such as AML later in life. These leukemias usually develop within 5 to 10 years of treatment and tend to be hard to treat.

Exposure to chemicals like benzene (a solvent used in the cleaning industry and in the making of some drugs, plastics, and dyes) may cause AML in adults and, rarely, in children. Chemical exposure is more strongly linked to an increased risk of AML than to ALL.

Some studies have found a possible link between childhood leukemia and household exposure to pesticides, either during pregnancy or early childhood. More research is needed to try to confirm these findings.

Weakened immune system

Children who are getting drugs to suppress their immune systems (mainly organ transplant patients) have a higher risk of certain cancers, such as lymphoma and ALL.

Other possible risk factors

A few studies have suggested that some childhood leukemias may be caused by a combination of genetic and environmental factors. For example, certain genes normally control how our bodies break down and get rid of harmful chemicals. Some people have different versions of these genes that make them less effective. Children who inherit these genes may not be as able to break down harmful chemicals if they are exposed to them. The combination of genetics and exposure might increase their risk for leukemia.

Many other possible risk factors have been studied, such as living near power lines or nuclear power plants, or having certain infections early in life. But so far, most studies have not found strong links between any other risk factors and childhood leukemia.